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  1. JDK
  2. JDK-8326385

[aarch64] C2: lightweight locking nodes kill the box register without specifying this effect

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    • b14
    • aarch64

      JDK-8319801 has introduced new C2 nodes cmpFastLockLightweight and cmpFastUnlockLightweight which use the box register as temp register, but the effects don't specify this behavior as a USE_KILL effect.
      It seems like the overwritten register content is never used, so, we currently don't see errors.

      There are several solutions:
      - Use a fixed register and USE_KILL effect.
      - Add a separate temp register.
      - Try to use one register less.
      - Ignore the bug and check that nothing can go wrong.

      In the long term, we can hopefully remove the box when the legacy locking mode is removed.

            rcastanedalo Roberto Castaneda Lozano
            mdoerr Martin Doerr
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